Lecture 10 - The Neurology Of Hearing And Balance Flashcards
What are the three parts of hearing system?
Outer ear, Middle ear and Inner ear
What are the structures of outer ear?
Pinna and External Auditory Canal
What are the functions of outer ear?
Sound waves are captured by the outer ear and funnelled through the external auditory canal to the tympanic membrane
Structures of Middle ear
Tympanic membrane, malleus, incus, stapes
What is the function of middle ear?
To convert the vibration in the air into some vibrations in the body so we can collect importante signals and process it
Sound waves can cause _______________ to vibrate.
Tympanic membrane
What are the functions of the three bones of the middle ear?
Transmit and amplify the vibrations to the oval window of the inner ear
What use the lever system principle in the middle ear, and what are the functions?
- Incus and stapes
- To save energy to have a higher efficiency using a lever system
- Amplify the signal and ensure the internal device can save space
What is the mechanism in middle ear?
The area in tympanic membrane is much larger than the oval window, so the pressure in the oval window is higher than that of tympanic membrane and that can amplify the pressure.
What can the bony structures in middle ear do?
It can selectively stop some parts to prevent the large sound from being sent to inner ear by tightening of tympanic membrane and increasing tendons in middle ear bones
What does inner ear convert?
Converts the mechanical signals into electrical signals
What is the structure for hearing in inner ear?
Cochlea
Why is cochlea needed?
- To save space
- To have a very long structure to capture different sounds with high-frequency sound travelling a shorter distance than low-frequency sound
Where in cochlea detect the high-frequency and low-frequency sounds?
- Sensors at the beginning of cochlea can detect high-frequency sound
- Sensors at the apex of cochlear (the end) will detect low-frequency sound
Where does liquid travel from and to in cochlea?
Liquid travels form oval window to round window in the cochlea, and that both structures are elastic that provides freedom to the perilymph inside
What is present in the cochlea?
Cochlear duct
What are the four hair cells in the cochlea?
3 outer hair cells and 1 inner hair cell
What are the functions of outer hair cells?
Backward connection from the brain and fine tune the sounds by pulling/ relieving the signals.
What are the functions of inner hair cell?
The main sensor for sound and transforming vibration into electrical signals
What are the two functions in inner ear?
- Fluid in the inner ear stimulate hair cells (nerve endings)
- Electrical impulses are sent from the hair cells along the auditory nerve to the brain
What is the procedure of converting mechanical waves into electrical signals?
- The mechanoreceptor induces influx of potassium ions (K+).
- Causing depolarization of cell.
- Further include influx of Calcium ions (Ca2+).
- Causing movement of vesicle to the membrane and release the neural transmitters, that will transform to electrical signals.
- The downstream processes are similar to neural synapse.
What can vibrate along the liquid environment in the inner ear?
Cilia
What can be detected by the brain if cilia can vibrate?
If cilia can vibrate, the small devices can be opened/ closed that cause change in the signals that can be detected by the brain.
What is energy transduction?
To transform some form of energy to another form of energy (and that goes through 5 kinds of energy in hearing)
Energy transduction procedure in hearing
- Auditory signal perceived from the ear
- Acoustic energy (air wave)
- Mechanical energy (membrane vibration)
- Hydraulic energy (fluid wave in perilymph)
- Mechanical energy (cilia bending)
- Electrochemical energy (neural activity)
- Temporal lobe in the brian
What are the five things in neural pathway in hearing?
- Cochlear nucleus
- Superior Olivary Complex
- Inferior colliculus
- Medial geniculate body
- Primary auditory cortex
What are the two types of cochlear nucleus?
Dorsal cochlear nuclei and Ventral cochlear nuclei
What does cochlear nucleus receive?
Electrical signal will arrive at cochlear nucleus for collecting different processing information?
What does dorsal cochlear nuclei do?
It makes sure the sound can quickly arrive at the brain to support/ find a shortcut to the brain
What does ventral cochlear nuclei do?
IT arrives at superior olivary nucleus to quickly analyse where the sound comes from that is detected bad calculated by superior olivary complex
What does superior olivary complex do?
- Binaural hearing: sound localisation, and intensity, timing
- Stapedius reflex (via CNVII): to send neural back to control and protect your ear structure
What does inferior colliculus do?
Startle reflex: immediately move/shake the body that can protect your body
Does startle reflex pass through the brain?
Startle reflex does not pass through the brain as the reflex happens very fast
Where is medial geniculate nucleus?
In thalamus
What does primary auditory cortex receive?
Both sides receive bilateral (binaural) information
What does the neurology of balance sense?
- sense of head and body movements: direction of movement and rotations, accelerations
- sense of head and body postures
How many semicircular canals are there i the peripheral vestibular system?
3 semicircular canals
What is the three basic head and neck movements that can be decomposed?
- Movement along the sagittal plane
- Movement along the coronal plane
- Movement along the horizontal plane
What are the three sensors to detect the 3 kinds of movements?
The three semicircular canals
What are the relationship between the three semicircular canals to each other (in terms of position)?
The three semicircular canals are perpendicular to each other.
What do the three semicircular canals capture?
They capture the 3D movements by linking neural activity with movement directions.
What is the sense of direction based on?
The sense of direction is based on combinatorial computations of different canals while the activity strength of different canals are different
What are the two different sensors to capture information related to movement?
Crista and Macula
What is crista responsible for?
It senses rotation and detects the location
What is the fluid movement in semicircular canal when you turn your head?
When you turn your head, the fluid in semicircular movement will turn to a direction that is different from the direction of head rotation.
When will crista be excitatory?
When crista is pushed to the certain direction of clockwise*, crista will be excitatory.
When will crista be inhibitory?
When fluid rotates anticlockwise, crista will be pushed to the certain direction and becomes inhibtory.
What is on the totuer layer of macula? What is its function?
Otoconia. Whenever we change the direction, the otoconia will move (being pulled back).
What is the function of macula?
Macula senses body posture and acceleration.
What in macula has the same mechanism as hair cells in the hearing system?
Stereocilia
What are the four different nuclei divided to give our body a balanced state in vestibular node?
- Superior Vestibular Nucleus
- Lateral Vestibular Nucleus
- Medial Vestibular Nucleus
- Inferior Vestibular Nucleus
What is the connection of superior vestibular nucleus?
Reciprocal connection with cerebellum
What is the function of superior vestibular nucleus?
Coordination of body movement and send information to the cerebellum in terms of motor errors
What is the output of lateral vestibular nucleus?
Output to lateral vestibulospinal tract
What is the function of lateral vestibular nucleus?
Vestibulospinal reflex and sends information to the body
What is the output of medial vestibular nucleus?
Output to medial vestibulospinal tracts
What is the function of medial vestibular nucleus?
Vestibulocollic reflex and sends information adjust information of head and neck
What is the function of output to cranial nerves for controlling eye movements?
Vestibulo-ocular nerves
What information does vestibular nucleus with the output to the nucleus?
Sends balance information to oculomotor nucleus, trochlear nucleus and abducens nucleus so that you can quickly observe surrounding thing and put body back to the correct position that controls eye movements
What does vestibulo-ocular reflex do?
It keeps us staring at one place?
Is vestibulo-ocular reflex lasting for a long time or a short time?
Instantaneous that is not using the brain to control it
What is the process of vestibulo-ocular reflex?
The fluid will activate the left vestibular nuclei that is connected to CN III and CN VI nucleus that controls the medial and lateral muscles repsectively to pull down the eyes in a clockwise direction.
